Light weight telescoping boom

ABSTRACT

A MULTI-SECTION TELESCOPIC BOOM HAS A SEPARATE, SINGLE ACTING HYDRAULIC CYLINDER FOR EXTENDING EACH MOVABLE SECTION AND A SINGLE CABLE FOR RETRACTING ALL OF THE SECTIONS. THE OUTERMOST SECTIONS HAVE SUPPORT FEET AT THEIR INNER ENDS WHICH STRADDLE THE CYLINDERS FOR THE NEXT INNER SECTIONS, THUS ELIMINATING GUARD PARTITIONS. A BIDIRECTIONAL FLOW DIVIDER SYSTEM IS USED TO SYNCHRONIZE EXTENSION AND RETRACTION OF THE SEVERAL SECTIONS, AND PRESSURE RELIEF VALVE IN THE SYSTEM ALLOW FOR RESYNCHRONIZATION.

March 20, 1973 J. T. HORNAGOLD LIGHT WEIGHT TELESCOPING BOOM 2 Sheets-Sheet 1 Filed Sept. 1, 1971 INVENTOR JOHN T. HORNAGOLD WW/fizz ATTORNE Y March 1973 J. T. HORNAGOLD LIGHT WEIGHT TELESCOPING BOOM 2 Sheets-Sheet 2 Filed Se t. 1, 1971 D L w R Y om f M mm W R w m W M w m E K VA k W F 3,721,054 LIGHT WEIGHT TELESCOPING BOOM John T. Hornagold, Waultesha, Wis., assignor to Bucyms- Erie Company, South Milwaukee, Wis. Filed Sept. 7, 1971, Ser. No. 178,027 Int. Cl. E0411 12/34; B66f 3/24 US. (ll. 52-115 7 Claims ABSTRACT OF THE DISCLOSURE A multi-section telescopic boom has a separate, single acting hydraulic cylinder for extending each movable section and a single cable for retracting all of the sections. The outermost sections have support feet at their inner ends which straddle the cylinders for the next inner sections, thus eliminating guard partitions. A bidirectional flow divider system is used to synchronize extension and retraction of the several sections, and pressure relief valve in the system allow for resynchronization.

BACKGROUND OF THE INVENTION This invention relates to telescopic booms for truck mounted cranes or the like, and particularly to a boom construction which has minimum cross-section size and weight for a given length and capacity. Boom cross-section size and weight are critical factors in designing truck mounted cranes and similar machines, particularly for small machines designed for highway travel where overall size and weight are limited and for very large machines where it is desired to have the ultimate capacity for a machine of given size and weight.

It has been conventional to use separate, double acting hydraulic cylinders for extending and retracting the several sections of telescopic booms, but this approach presents problems with respect to size and weight. The basic problem is that the cylinder pistons must be large enough to present sufiicient area for the return stroke, and as a result overall cylinder size and weight are considerably greater than single acting cylinders or rams.

Another factor which has significantly increased the weight of conventional booms is the guard and support partitions which have been used in each movable section to support the next succeeding outer section. That is,the hydraulic cylinder for each section must extend all the way to the front of the section it moves so that the cylinder can take axial loads. The cylinder usually lies immediately above the floor of the section it is moving, and the next outer section is made small enough vertically so that it clears the cylinder during extension and retraction. Some means must be provided, however, to support the outer section and to prevent it from damaging the cylinder. Heretofore, it has been conventional to provide a partition for each intermediate section which lies above the actuating cylinder and extends for the entire length of the section. While such partitions serve the necessary purposes, they add considerable weight.

Another problem which occurs in multi-section telescopic booms with individual actuating cylinders is the necessity for synchronizing several sections. That is, it is desirable to have the sections extend and retract simultaneously to maintain the overall tapered configuration of the boom at any length. It is necesary to provide means to accomplish this without unnecessary weight or expense and, since no such means are one hundred percent effective because of leakage and other reasons, it is also necessary to incorporate some way of resynchronizing the several sections.

nited States Patent SUMMARY OF THE INVENTION It is the general object of this invention to provide a telescopic boom construction of minimum size and weight for a given capacity. It is possible, for example, using the construction shown in the preferred embodiment herein, to reduce overall boom weight by as much as ten percent for a given length and capacity.

One specific object of the invention is to provide a telescopic boom construction in which separate, single acting cylinders are used to extend the movable sections while a single cable is used to retract all of the sections, all of which results in substantial reductions in cross-section size and weight. Another specific object is to provide a boom construction in which conventional guard and support partitions are replaced by feet at the inner ends of the outermost sections which straddle the cylinders for the next succeeding inner sections. Still another specific object is to provide a construction in which a bidirectional flow divider system is used to synchronize extension and retraction of the several sections, the system allowing for resynchronization as necessary. Other objects and advantages will appear from the descrition to follow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat schematic side view in elevation showing a boom constituting a preferred embodiment of the invention, the boom being shown in a fully retracted position,

FIG. 2 is a view similar to FIG. 1, but showing the boom fully extended,

FIG. 3 is an end view in cross section through the plane 33 shown in FIG. 1,

FIG. 4 is an end view in cross section through the plane 44 shown in FIG; 2, and

FIG. 5 is a schematic diagram showing the hydraulic circuitry for the boom of FIGS. 1-4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment is a four-section boom which includes a non-extensible base section 1, a first or inner extensible and retractable section 2, a second or intermediate extensible and retractable section 3 and a third or outer extensible and retractable section 4 which carries a suitable tip assembly 5. In the preferred embodiment, the sections 1-4 are all of substantially solid, rectangular box construction; but it will become obvious that lattice box or other constructions or configurations could be used within the purview of the invention, and the term box is intended to cover all appropriate configurations. The particular boom shown has been designed for a truck mounted crane (not shown) and the base section 1 is arranged to be vertically pivotally mounted on the revolving frame at 6. It will also be obvious, however, that the boom might be mounted on any other type of carrier or support, and need not be pivotal.

A hydraulic actuating cylinder 7 is provided for extending the section .2; and has its cylinder end pinned near the inner end of section 1 and its rod end pinned near the outer end of section 2. An actuating cylinder 8 is used for extending the section 3; and has its cylinder end pinned at the inner end of section 2 and its rod end pinned near the outer end of section 3. An actuating cylinder 9 is used to extend the section 4, and has its cylinder end pinned at the inner end of section 3 and its rod end pinned near the outer end of section 4-. Each of the cylinders 7-9 extends just above and along substantially the entire length of the floor of the section which it serves to extend. Each of the cylinders 7-9 is a singleacting hydraulic cylinder which is operable only to extend the associated section, and the hydraulic connections for the several cylinders will be described below.

As can be seen most clearly in FIGS. 2 and 3, the section 2 is provided at its outer end with an axially short, transverse support bar which extends across the section 2 immediately in front of and above the rod end of its cylinder 7 and serves to support the underside of the section 3 during extension and retraction of the latter. The section 3 is provided at its outer end with a similar support bar 11 which supports the section 4. In the preferred embodiment shown, the bars 10 and 11 are unitary, U-shaped members with their side legs welded or otherwise fixed to the side walls of the associated sections and their bight portions extending entirely across the open section ends to serve as the actual support bars; but other constructions are possible. It is not strictly necessary, for example, to have support bars that extend entirely across the sections and L-brackets fixed to the section side walls could be used to support the bottom edges of the next outer section. All that is required is some sort of Support means at the outer end of each intermediate section to support the next outer section.

The section 3 is provided at its inner end with opposite, downwardly extending feet 12. which straddle the cylinder 7 and have inwardly turned bottom portions which ride along the floor of the section 2 to support the inner end of the section 3 during extension and retraction. The inner end of the section 4 is provided with similar feet 13 which ride along the floor of the section 3 and support the inner end of the section 4. Thus, the section 3 is supported during extension and retraction at two points, by the support bar 10 on the section 2 and its own feet 12, and these two supports enable the section 3 to be extended and retracted without engaging the cylinder 7. The section 4 is similarly supported and prevented from damaging the cylinder 8 by the support bar 11 and feet 13. The supports thus provided are quite effective, and yet eliminate the substantial extra weight of the usual guard partitions which would conventionally extend along the entire lengths of the sections 2 and 3. The section 2 needs no such support because it does not have to clear a cylinder for a preceding section, and it thus rides directly on the fioor of the section 1. While the form of support shown and described is particularly suitable for use in connection with the other features to be discussed below, it will be apparent that this arrangement might be used in booms utilizing conventional double acting cylinders for extension and retraction.

As previously indicated, the cylinders 7-9 serve only to extend their respective sections. Retraction of all of the movable sections 2-4 is accomplished by means of a cable 14, which may be single or multiple strand, which leads from a hydraulically driven winch 15 mounted at the rear end of the section 1 and is connected only to the inner end of the section 4. Using single acting cylinders for extension with a cable retract in this manner affords a very substantial reduction in weight and/or size since the cylinders 7-9 can be substantially smaller and lighter than conventional double acting cylinders and the cable 14 adds very little weight.

The hydraulic circuitry for the boom is shown in FIG. 5. A single or multiple pump 16 serves as a fluid source and draws from a common reservoir 17, the pump 16 and reservoir 17 together serving as fluid supply and return means. The pump 16 leads to a conventional manually operated directional control valve 18, and a relief valve 19 provides for overall system relief.

One of the motor ports of the valve 18 is connected to the inlet of a first flow divider 20 which has output lines 21 and 22. The flow divider 20 is of any conventional spool type, but is set so that two-thirds of the output of the valve goes into the line 22 while only onethird goes into the line 21, valves which can be set in this fashion being well known. The line 21 leads directly to the cylinder 7, which thus receives one-third of the output of the pump 16. The line 22, however, leads to the inlet of a second flow divider 23 which has output lines 24 and 25. The flow divider 23 is of the same type as the flow divider 20, but is set so that the output in the lines 24 and 25 is equal. The line 24 leads to the cylinder 8, and the line 25 leads to the cylinder 9, so that these cylinders also each receive one-third of the output of the pump 16. Since the cylinder ends of the cylinders 8 and 9 move inwardly and outwardly, the lines 24 and 25 are mounted on conventional reels 26 which are mounted at the inner end of section 1 and include hydraulic passages.

When the valve 18 is shifted downwardly from the position shown in FIG. 5, so that fluid under pressure is delivered to the valve 20, the cylinders 7-9 will all extend at the same rate because each is receiving an equal portion of the flow from the pump 16. This is of course based on the assumption that the cylinders 7-9 are of equal size, but the same concept can be used with different size cylinders by appropriate adjustment to the flow dividers 20 and 23.

As previously indicated, retraction of the cylinders 7-9 is accomplished by means of the cable 14 and winch 15, the latter being powered by a hydraulic motor 27. When the valve 18 is shifted upwardly as shown in FIG. 5, pressurized fluid will be delivered to the motor 27 which will cause the winch 15 to reel in the cable 14. The lines leading to the cylinders 7-9, however, include conventional counterbalance valves 28 which ordinarily prevent retraction and must be piloted open. For this purpose, a pilot line system 29 leads from the pressure line 30 which goes to the motor 27 and is branched to lead to the three counterbalance valves 28, the branches for the cylinders 8 and 9 leading through the reels 26. This arrangement insures that the cylinders 7-9 will retract only when intended by the operator, as evidenced by shifting of the valve 18.

Fluid returning from the cylinders 7-9 returns through the fiow dividers 23 and 20 in the same proportion as for extension, as the result of which the three cylinders will retract in synchronization. In actual practice, however, the cylinders are likely to become desynchronized for various reasons such as leakage, etc. As a result, it is entirely likely that one or two cylinders will bottom out before the rest, and some means must be provided to allow full retraction of the remaining cylinder or cylinders so that the several cylinders will be resynchronized. This is accomplished in the preferred embodiment by means of three conventional pressure relief valves 31, one connected to the line 21, one connected to the line 24, and one connected to the line 25. Each of the valves 31 leads to a branched common relief line 32 leading to the reservoir 17; and the motor 27 is also connected to the line 32 for the return of fluid. When any one or two of the cylin ders has bottomed out, there will be an increased pressure in the line leading back from the remaining cylinder or cylinders, and this will cause the associated valve or valves 31 to open so that return fluid can be passed directly to the reservoir 17, as the result of which the remaining cylinder or cylinders can fully retract. At the conclusion of retraction, therefore, all of the cylinders will be bottomed out and thus resynchronized.

The preferred embodiment shown and described provides an extremely light weight boom with synchronized operation. As indicated above, however, various changes might be made in structure and application without departure from the spirit of the invention. The basic boom may of course be used in various environments and may include more or less sections. The support feet for the outermost sections might be used where there are either single or double acting cylinders. Wet rod cylinders might be substituted for the dry cylinders shown. While the twostage, spool flow divider system shown is preferred in view of the components presently commercially available, other bidirectional flow dividers systems, such as three gear pumps keyed to a common shaft, might be used to replace the two flow dividers 20 and 23. In view of the many possible modifications, the invention is not intended to be limited by the showing or description herein, or in any other manner, except as may specifically be required.

I claim:

1. In a telescopic boom having at least two extensible and retractable box sections wherein an actuating cylinder for the inner of the two sections extends along and above the floor of the inner section to a point near the forward end thereof, and the outer of the two sections is telescopically received in the inner section and has a floor that is spaced above the floor of the inner section a distance sufficient to accommodate the cylinder, the improvement wherein there is a support means at the outer end of the inner section which engages the underside of the outer section to support the same as it is extended and retracted; and the outer section is provided at its inner end with opposite, downwardly extending feet which ride along the floor of the inner section on opposite sides of the cylinder to support the inner end of the outer section during extension and retraction thereof.

2. A boom according to claim 1 wherein: there is a second actuating cylinder for the outer section; and both cylinders are single acting and are operable only to extend the respective sections; and there is a cable attached to the outer section to retract both sections.

3. A boom according to claim 2 wherein: there is a bidirectional flow divider system connected between both cylinders and a fluid source and reservoir, said system serving to proportionally divide flow from the source between the cylinders so that the two sections extend in synchronism and to proportionally admit return flow from both cylinders so that the two sections retract in synchronism.

4. A boom according to claim 1 wherein there is: a plurality of at least two extensible and retractable sections with the innermost through the second outermost of said sections having said support means at their outer ends and the outermost through the second innermost of said sections having said feet at their inner ends; a separate, single-acting hydraulic actuating cylinder for each section, each cylinder being operable only to extend its associated section; a cable attached to the outermost section and operable to retract all of the sections; a fluid supply and return means including a pump and a reservoir; and a bidirectional flow divider system connected between the fluid supply and return means and all of the cylinders,

6 said flow divider system serving to proportionally transmit fluid from the pump to all of the cylinders so that all of the sections extend in synchronism and also serving to proportionally admit fluid returned from all of the cylinders to the reservoir so that all of the sections retract in synchronism.

5. A system according to claim 4 wherein: the flow divider system has a plurality of output lines, one output line leading to each cylinder; and there are an equal plurality of pressure relief valves, one relief valve leading from each output line, all of the relief valves leading to the reservoir.

6. A system according to claim 5 wherein: the cable is connected to a winch driven by a hydraulic motor; and the pump leads to a directional control valve which is shiftable to deliver fluid under pressure alternatively to the flow divider system or to a pressure line leading to the motor; and each of the output lines includes a counterbalance valve which normally blocks return flow from the associated cylinder; and there is a pilot line system leading from the motor pressure line to all of the counterbalance valves.

7. A system according to claim 6 wherein: there are three boom sections and cylinders; and the flow divider system includes a first two way flow divider that has a first output line leading to one cylinder and a second output, said first flow divider being adapted to deliver onethird of its output to the first output line and two-thirds to the second output; and there is a second two way flow divider connected to the second output, said second flow divider being adapted to deliver equal outputs to two output lines which lead, respectively, to the other two cylinders.

References Cited UNITED STATES PATENTS 2,891,383 6/1959 Troche et al 52115 X 3,398,492 8/1968 Nansel 52-l 15 3,398,645 8/1968 Nansel 52-115 X PRICE C. FAW, JR., Primary Examiner US. Cl. X.R. 

